Various fuel injection control devices have been proposed for learning a deviation amount in a vehicle fuel injection characteristic. For instance, U.S. Pat. No. 6,907,861 (i.e., Japanese Patent Publication No. 2005-036788) proposes a fuel injection control device for a vehicle with a diesel engine. When the clutch is disengaged, a deviation amount of a fuel injection characteristic is learned. More specially, when the learning condition is met, a single fuel injection is performed and an increase amount of rotation of the output shaft of the engine is detected. Since the clutch is disengaged and the output shaft is disconnected from the driven shaft, the increase amount of the rotation has a strong correlation with a fuel quantity actually injected. Thus, this procedure provides an accurate measurement (learning) of any deviation in fuel injection characteristic.
The above control device, however, has certain disadvantages. Specifically, there are relatively few opportunities for learning since learning is performed only when the output shaft for the diesel engine is disconnected from the drive wheels. For instance, if this system is incorporated in a vehicle with an automatic transmission, learning occurs when the shift lever is in a neutral position. Thus, there are relatively few opportunities for learning. (It is understood that if this learning processes occur in a state other than when the shift lever is in the neutral position, the learning accuracy can be degraded. This is because if the same quantity of fuel is injected, the output shaft rotation caused by the fuel injection varies depending on the connection state between the engine output shaft and the driven shaft through a torque converter.)
Thus, there exists a need for a fuel injection control device that overcomes the above-mentioned problems in the conventional art. As will be explained, the following disclosure addresses this need as well as other needs, which will become apparent to those skilled in the art.